Which method of heating your conservatory is best?
Conservatory heating is a necessary expense if you wish to use your conservatory in the winter months or Autumn/Spring on overcast days or in the evenings. The are many different ways to heat your conservatory and we will look at some of them here, investigating the relative pros and cons of each method including purchase prices, installation costs and running costs where possible. Below is a table summarizing some of the methods of heating your conservatory along with approximate costings on the assumption of a 10m2 area.
| Conservatory Heating Method | Approximate Purchase Cost | Approximate Running Cost per Hour |
|---|---|---|
| 2kw Fan heater | £25 | 46p |
| 2kw Oil Filled Radiator | £85 | 46p |
| 2kw Electric panel heater | £120 | 54p |
| Connect to existing home central heating system | £550 | 7.6p |
| Split unit air conditioning system as heater | £1750+ | 13.6p |
| Air source heat pump + underfloor heating | £5000+ | 11.5p |
Costs are based on 23p per kw/h assuming unit is running at maximum capacity (in reality the unit will run at maximum until a comfortable temperature is reached and then switch off or reduce consumption to maintain temperature, reducing cost per hour usage).
Reasons to heat your conservatory
- Maybe you use your conservatory as a breakfast room in which case it needs to be warm in morning all year round.
- If your conservatory is used throughout the day during Winter it is a good idea to have a heating solution that either has a very constant temperature or can be topped up during the day if required.
- Perhaps you keep sub-tropical or tropical plants in it which could not withstand the freezing temperatures we get in the winter here. Then it must not drop below a certain temperature.
Below are some specific ways of heating your conservatory.
Fan heater
Readily available and inexpensive to buy, can be a good temporary stop gap for the coldest of days but not recommended to be used at all times.
Pros
Cons
- Cheap
- Portable
- Instant heat
- Noisy
- Expensive to run
- Air flow can be irritating.
Oil filled radiator
These are also readily available and a better alternative to the fan heater as they retain heat and act more like a conventional radiator.
Pros
Cons
- Relatively cheap
- Comfortable radiant heat
- Quiet
- Large
- Running costs can be high
Electric panel heater
Buy and install a simple low profile electric panel heater.
Pros
Cons
- Easy to install- plug it in
- Fairly low cost
- Plenty of heat available – up to 3kW per unit
- Quick to heat up
- Slim line and quiet
- Running costs can be high
Central heating system
You could simply connect a new radiator to an existing central heating system. Check with your conservatory supplier or local building officers to make sure this is allowed. If you have an efficient boiler already then this method will have a very low running cost. It is a requirement that the radiator you place in the conservatory has its own thermostatic control and can be turned off. For optimum heat circulation it is suggested to install the radiator near the dwarf wall though this is not always possible nor indeed convenient.
Pros
Cons
- Cheaper to run than electric direct heating alternatives
- Comfortable radiant heat
- Slim line and quiet
- Higher up front cost
- Control of temperature may be an issue depending on how the thermostatic control of heat in the rest of the house is set-up. Your house and conservatory will heat up and cool down at different rates. This could be overcome with smart heating controls.
Tubular Heating
This is commonly used in outside rooms, sheds and greenhouses where the desire is to prevent the room from going below zero which could damage plants, pipes and other items.
Pros
Cons
- Frost protection kits available.
- Designed to operate in damper conditions e.g. glass house or garden shed.
- Splash proof if conservatory used for lots of plants that need watering.
- Low initial cost.
- Low power only really usable for frost protection.
Air source heat pump with underfloor heating
Heat pumps come in two varieties air source and ground source. This defines where they extract the heat from. Heat pumps are commonly used as the source for an underfloor heating system due to the low temperature water they produce. They operate using the refrigeration cycle. The inside of a fridge is cold and the back heat exchanger is warm. In a heat pump the outside world is cooled down and the heat is pumped into the inside. The advantage is that typically for every 1 unit of electricity 4 units of heat can be brought inside.
Pros
Cons
- Outside unit can be wall or floor mounted.
- Low running costs ~ 13.5p per hour for 2kW of heating assuming 4 to 1 heat gain.
- Comfortable underfloor radiant heat.
- Expensive to install and can be retrofitted but ideally should installed on the initial building of a conservatory due to the pipes laid in screed.
- Outside unit can be noisy and relatively large.
Direct electric underfloor heating
An electric heating mat is placed underneath tiles or within the floor screed. A separate controller monitors room and floor temperature adjusting the mat temperature accordingly.
Pros
Cons
- Unobtrusive, an electric underfloor heating mat is slim in profile and can be retrofitted fairly easily.
- Comfortable underfloor radiant heat.
- Lower cost to install than an underfloor air source system.
- Expensive to run.
Air conditioning
An air-to-air split system professionally installed and wall mounted can be used for heating and cooling. Air conditioning units are usually selected on their cooling capacity rather than their heating capabilities. Therefore running costs are tricky to calculate.
Pros
Cons
- Can be used for cooling and heating.
- Easy to control and pretty much on-demand heating or cooling.
- Expensive to install.
- Outside unit can be noisy and relatively large.
- Blown air flow can be irritating.
How much heating do I need?
The amount of heating required depends on:
- Size of conservatory
- Insulation properties of the glass/frame – U value
- Required temperature differential – temperature inside to outside
To complicate matters the shape of the conservatory and weather conditions such a wind speed will effect the heat loss but they are not considered here.
Heat loss is modelled using the following equation:
- Heating required (watts) equals U value * Area * temperature difference
Area is the glass area of the conservatory plus 1/3rd of the area of the connecting wall. It gets more complicated if the conservatory is constructed using different glazing options (e.g. roof) or is angled. So for a conservatory with a 10m2 floor area and 2.4m high walls and slightly sloping roof one would have an area of 37.3m2.
Single glazing has a U value of around 5 or more. Old style double glazing is about 3. Newer low-e coatings are closer to 2 with triple glazed argon filled (read expensive) units as low as 0.4.
Assuming you wish to have a minimum temperature of 18C in the daytime (with say an outside temperature of zero) we can then calculate the required best case heating requirement at about 2kW. With low-e glass it would be about 1.3kW.
Note: A dealer of conservatories or heating unit will be able to input more realistic figures but this is just ballpark. It allows us to compare different methods of heating the conservatory for price on a very typical size conservatory.
It’s clear that a good way of heating your conservatory is to stop any heat within the structure escaping in the first place. However, extremely high performance glass (such as tripled glazed argon filled low-e variety) or a replacement solid conservatory roof can be very expensive and depending on your conservatory usage you may never recover the investment in reduced heating bills.
Conservatory heating conclusions
There are a few different ways of heating your conservatory. Typically the lower upfront cost the higher the running cost. Ultimately its a hard call as to how much to spend on well insulated glass and how much to spend on efficient heating systems. Either way it’s always best to factor in costs for efficient heating in the initial conservatory installation.
Hopefully this breakdown of methods and costings has given you the information to make a better informed decision.